1. Field of the Invention
The present invention relates to a method and an apparatus for analyzing and evaluating a surface state of a semiconductor wafer, and more particularly, to a method and an apparatus for accurately and quantitatively analyzing/evaluating a growth state of grains on the surface of a semiconductor wafer, in which the grain growth is automatically calculated using an image file of the surface of the semiconductor wafer that is scanned by scanning electron microscopy (SEM).
2. Description of the Related Art
As semiconductor devices become smaller, the elements of the device, such as a capacitor, also become correspondingly smaller. Since the capacitance of the capacitor is proportional to a surface area of a capacitor electrode, semiconductor manufacturers and designers must somehow compensate for the reduced size and capacitance of these smaller capacitors. Accordingly, a focus of the manufacturing process is to obtain a larger surface area for the capacitor electrode.
One typical manufacturing method for increasing the surface area of the capacitor electrode is to grow hemispherical grains (HSGs) on a surface of the capacitor electrode. One particular manufacturing method increases the surface area of the electrode itself by forming a one cylinder stack (OCS)—type capacitor electrode on which the HSGs are grown. The introduction of the OCS process combined with the HSG process increases the surface area of the capacitor electrode, thereby obtaining a large capacitance of the capacitor electrode.
The surface area of the OCS-type capacitor is smaller in an upper distal portion thereof and larger along the sidewalls thereof. During the manufacturing process for forming the OCS-type capacitor, the degree of HSG growth directly affects the ability to achieve a target capacitance, and therefore, a method for measuring a thickness of the HSGs is used and monitored. However, that method is ineffective in those cases where a polysilicon thin film, on which the HSGs of a measurement test portion may be grown, is etched after introducing the OCS process.
To overcome this problem, a method for measuring light reflectivity within a cell has been proposed, but this method suffers a drawback in that it lacks the ability to precisely discriminate between elements of the semiconductor device.
Meanwhile, a scanning electron microscopy (SEM) method is widely used to precisely scan the surface state of the semiconductor wafer and analyze a manufacturing defect. When used in conjunction with measuring the growth degree of HSGs on a semiconductor wafer, the SEM simply scans the growth state of the HSGs grown on the OCS-type capacitor and then displays a scanned image. Therefore, the operator must directly view the displayed image and determine the growth degree of the HSGs empirically. As can be expected, such an empirical measuring method needs much time and effort, and additionally, it is difficult to accurately evaluate the quantitative growth degree of the HSGs because of the vagaries and inconsistencies inherent in a process involving human intervention.